Description (Adapted from Application): The long-term of this study are to understand the functions of vitamin B12 compounds in enzymatic reactions and as therapeutic agents in terms in terms of their chemical properties. Some specific goals of the research project are to investigate the interactions of nitrogen oxides, N0 and N20, with vitamin B12 (cobalamin) compounds in vitro in order to understand their effects on enzymatic reactions of methionine synthase B12-MS, and their effectiveness for sequestering trauma-induced NO in vivo. One hypothesis is that redox reactions of NO and N20 with the Co(II) and Co(I) forms of cobalamin can affect enzyme functioning. Specific studies include the complexes formed and the redox behavior of systems of NO, N20 with corrinoid compounds in three oxidation sites using electrochemical measurements, UV-Vis spectroscopy, resonance Raman spectroscopy (RRS), surface enhanced resonance (EPR) spectroscopy. Nitrogen species formed as reaction products will be investigated by GC-MS. The reductive cleavage mechanism for the activation for the activation of methylcobalamin and adenosylcobalamin will also be studied. The aims is to measure equilibrium and adenosylcobalamin will also be studied. The aim is to measure equilibrium binding constants, redox reaction rates, and electrochemical reduction potentials for cobalamin redox couples and to determine the structure of NO binding in their nitrosyl complexes. These results should help in understanding how NO and N20 work in deactivating MS-B12 and how cobalamine detoxify organisms with elevated levels of NO. Experiments will also investigate the solvent and pH effects of the equilibrium and kinetic properties of the complexes.